The present invention relates to an apparatus and method for reliably, precisely, and quickly classifying and sorting crystalline objects according to shape.
Synthetic diamonds are crystalline objects that are used as abrasives. The quality of industrial diamonds for use in abrasive applications is dependent on their shape. Regular diamonds, like other cubic-system crystals, take the form of cubes, octahedrons, or shapes intermediate between cubes and octahedrons. The intermediate shapes are the fourteen-faced solids which are obtained by truncating the corners of either a cube or an octahedron. In order to have optimal abrasive properties the shape of a diamond should lie midway between a cube and a octahedron.
Diamonds produced by ordinary synthetic methods exhibit a wide range of shapes. By changing the parameters of the production process the operator may exercise some control over shape in response to feedback information regarding diamonds previously produced. Because of market demand for the preferred shapes, the synthetic diamonds produced by ordinary methods are sorted by shape before they are sold. However there presently is no means for classifying and sorting synthetic diamonds which is simultaneously reliable, precise, and quick.
It is known to classify diamonds by eye into nine shape groups lettered A through I, A being an octahedron and I being a cube. Shapes C, D, and E are preferred for diamond abrasives. This method is imprecise and not practical for sorting production quantities of diamonds. For sorting of diamonds during production a shaker table is used. The shaker table separates the diamonds into eight classes designated Cup 1 to Cup 8. Cup 1 diamonds roll most easily and are the most desirable, whereas Cup 8 diamonds roll poorly and are least desirable. Cup 1 diamonds consist of a large percentage of shapes C, D, and E. However, the shaker tables are unpredictable in their operation and the same diamond will not always go into the same cup. The distribution of diamonds into the various cups is difficult to characterize and depends on peculiarities in the construction of the shaker table in a manner that is neither easily understood nor precisely reproducible.
For the foregoing reasons, there is a need for a means of reliably, precisely, and quickly classifying and sorting crystalline objects such as synthetic diamonds which can be used in both analytic and production applications.